Tire construction with flattened summit and circumferential reinforcement

ABSTRACT

A tire constructed with a plurality of reinforcement belts is provided. At least one of the reinforcement belts extends along the axial width of the tire summit and is constructed according to an equilibrium curve that is flat throughout the summit. The reinforcement belts include cable reinforcements that are substantially parallel to the equatorial plane. Substantial reductions in the tension experienced by the cables can be achieved to provide, as a result, improvements in e.g., tread wear.

PRIORITY STATEMENT

The present application is a Divisional Application of and claimspriority to U.S. patent application Ser. No. 14,371,266 filed on Jul. 9,2014, which is a § 371 Application of PCT/US2012/021425, filed Jan. 16,2012, all of which is incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The subject matter of the present invention relates generally to a tirehaving circumferentially-oriented reinforcements in the summit and thatis constructed according to an equilibrium curve that is flat in thesummit as further described.

BACKGROUND OF THE INVENTION

Equilibrium curves are used in tire design to define the geometry of thetire particularly, e.g., the shape of the carcass, which is areinforcing structure that extends through the crown or summit of thetire and between the bead regions located on each side of the tire. Uponthe inflation and loading of the tire, the equilibrium curve used indesigning and constructing the tire will substantially determine thestresses that will be experienced by belts in the summit. Theequilibrium curve also helps determine the exterior profile of the tireas well as its potential for wear during use.

Conventionally, the equilibrium curves used for tire design andconstruction have typically used a three-ply membrane model thatprovides significant curvature for the tire along the summit region. Thecarcass is usually constructed to follow the shape of the equilibriumcurve. Belts in the summit that are placed over, or radially outside of,the carcass adopt much of their shape and, therefore, curvature from theshape of the carcass.

As used herein, “droop” refers to the difference in position, along theradial direction, between the center (i.e. at the equatorial plane) of abelt in the summit and the edge of such belt. As the tire rolls throughthe contact patch (the portion of the tire in contact with the road),the tire flattens in the contact patch when under a load. Droop in asummit belt contributes to the amount of tension experienced by the beltas it flattens in the contact patch. Such belt tension provides alimitation on the overall width to which a tire can be designed andconstructed. This width limitation is undesirable because in certainapplications a wider tire can provide performance advantages. Forexample, for certain commercial truck tire applications, a wide tire canreplace a pair of narrower tires and provide improvements in fuelefficiency.

Additionally, droop in a summit belt leads to differences in rollingradii. More specifically, the radii from the axis of rotation for adrooping summit belt will likely be different at various locations alongthe axial direction. This difference can, in turn, result in differentaverage longitudinal stresses along the contact patch between the centerand shoulder regions of the tread so as to provide undesirabledifferences in wear rate across the tread width. Also, less evenlydistributed contact pressure between the tire and road surface can occuracross the contact patch so as to further aggravate differences in wearrate across the tread width.

Accordingly, a tire and/or equilibrium curve for a tire that can be usedto avoid or minimize droop would be useful. More specifically, anequilibrium curve that allows designing and constructing wider tireswith improvements in performance would be beneficial. Such anequilibrium curve that can allow e.g., the use of wider summit belts andtread widths with improvements in tread wear would also be particularlyuseful.

SUMMARY OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In one exemplary embodiment, the present invention provides a tiredefining axial, circumferential, and radial directions. The tire alsodefines equatorial and meridian planes and has a summit regionpositioned between sidewall portions of the tire. The tire includes acarcass extending between the sidewall portions and through the summitregion of the tire; a working ply positioned radially outside of thecarcass and extending along the axial direction of the tire; and aplurality of reinforcement belts positioned radially outside of thecarcass and positioned in the summit region of the tire. At least one ofthe reinforcement belts extends along the axial direction and throughthe equatorial plane, and at least one of said reinforcement beltsextends between the sidewall portions of the tire. The reinforcementbelts each include a plurality of circumferentially-oriented cables andeach have a straight profile within a meridian plane of the tire. Atread portion is positioned radially outside of the reinforcement beltsand extends through the summit region and between the sidewall portionsof the tire.

In another exemplary embodiment, the present invention provides a tiredefining axial, circumferential, and radial directions. The also definesa meridian plane and has a summit region positioned between sidewallportions of the tire. The tire includes a carcass extending between thesidewall portions and through the summit region of the tire, a workingply positioned radially outside of the carcass and extending along theaxial direction of the tire, and at least one reinforcement beltpositioned radially outside of the carcass and in the summit region ofthe tire. The at least one reinforcement belt has at least one axiallyouter end that extends to one sidewall portion of the tire and anotheraxially outer end extending to the other sidewall portion of the tire.The reinforcement belt includes a plurality ofcircumferentially-oriented cables and has a flat profile within ameridian plane of the tire. A tread portion is positioned radiallyoutside of the reinforcement belts and extends through the summit regionand between the sidewall portions of the tire.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 provides a cross sectional view, taken along a meridian plane, ofan exemplary embodiment of a tire according to the present invention.

FIG. 2 provides cross sectional view, taken along a meridian plane, ofanother exemplary embodiment of a tire according to the presentinvention.

FIG. 3A is a plot of simulation data for both the exemplary embodimentof FIG. 1 as well as a known tire construction.

FIG. 3B is a plot of simulation data for both the exemplary embodimentof FIG. 2 as well as a known tire construction.

FIG. 4 is plot of simulated vertical stiffness data for of the exemplaryembodiments of FIGS. 1 and 2 as a percentage of the vertical stiffnessfor a known tire construction.

FIG. 5 is a simulated plot of the footprint for the exemplaryembodiments of FIGS. 1 and 2 as well as known tire construction.

FIG. 6 is a plot of a portion of an equilibrium curve as used inexemplary embodiments of the present invention.

The use of identical or similar reference numerals in different figuresdenotes identical or similar features.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a tire constructed with one or morereinforcement belts that extend along the axial direction in the tiresummit and are constructed according to an equilibrium curve that isflat throughout the summit. The one or more reinforcement belts includecable reinforcements that are substantially parallel to the equatorialplane. Substantial reductions in the tension experienced by the cablescan be achieved to provide, as a result, improvements in e.g., treadwear. For purposes of describing the invention, reference now will bemade in detail to embodiments and/or methods of the invention, one ormore examples of which are illustrated in or with the drawings. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features or steps illustrated or describedas part of one embodiment, can be used with another embodiment or stepsto yield a still further embodiments or methods. Thus, it is intendedthat the present invention covers such modifications and variations ascome within the scope of the appended claims and their equivalents.

The following terms are defined as follows for this disclosure:

“Axis of rotation of the tire” is the axis around which the tire rotatesduring its normal use.

“Axial direction” refers to a direction parallel to the axis of rotationof the tire and is designated with the letter A.

“Radial direction” is orthogonal to the axial direction and extends inthe same direction as any radius that extends orthogonally from theaxial direction. The radial direction is designated with the letter R.

The “circumferential” direction corresponds to the periphery of the tireand is defined by the rolling direction of the tire.

“Circumferentially-oriented” as used with regard to certain beltreinforcements of the present invention means either parallel to theequatorial plane or making an angle of 5 degrees or less with theequatorial plane.

“Rolling tread width” is the width of the tread on the tire that makescontact with the ground as the tire rolls through the contact patch.

“Summit,” “tire summit,”or “summit region” refers to that portion of thetire between the sidewalls and radially outside of the carcass of thetire. The summit, therefore, includes e.g., the tread portion of thetire and belts located between the tread portion and the carcass. Thesummit is also sometimes referred to as the crown of the tire.

“Equatorial plane” is a plane that is perpendicular to the axis ofrotation of the tire and bisects the summit of the tire into two halves.The equatorial plane is designated with EP.

“Meridian plane” is a plane containing the axis of rotation of the tire.

FIG. 1 provides a cross-sectional view, taken along the meridian plane,of tire 100 in an exemplary embodiment of the present invention. Tire100 includes a summit 110 that extends between the top of sidewallportions 108 and is bisected by the equatorial plane EP. As will beunderstood by one of skill in the art, radially inward of the sidewallsportions is bead section of the tire (not shown) that includes a beadcore and is used to seat tire 100 onto a wheel or rim. Tire 100 alsoincludes a tread portion 112. The present invention is not limited toonly the tread configuration shown and, instead, can include multipleribs, blocks, and/or combinations thereof. Asymmetrical designs aboutthe equatorial plane are also contemplated.

A carcass 106 extends between the sidewall portions 108 and through tiresummit 110. Carcass 106 is typically anchored in the bead sections andhelps contain the outward forces provided by air pressure within tire100. Carcass 106 may include multiple reinforcements such as e.g., cordsoriented along the radial direction and/or at angles therefrom. Radiallyinward to carcass 106 is a pair of inner liner layers 102 and 104. Suchlayers are constructed from e.g., an air impermeable material to retainair within tire 100.

Tire 100 also includes a breaker belt 118 that is positioned radiallyoutward of carcass 106. In general, breaker belt 118 helps to protectagainst punctures or other forces that might damage carcass 106 and/orinner layers 102 and 104. Working plies 120 and 131 are positionedradially outward of breaker belt 118 and radially inward of treadportion 112. By way of example, working plies 120 and 131 providestrength and stiffness to tire 100 including stiffness with regard tosteering.

For the exemplary embodiment of FIG. 1, tire 100 includes areinforcement belt 130 that is positioned between plies 120 and 131.Reinforcement belt 130 has an axial width that is slightly larger thanbreaker belt 118, in this particular embodiment, but does not extend toreinforcement belts 122 and 124, which are positioned radially outsideof working ply 131. However, other configurations for the axial widtharrangement of belt 130 relative to belts 122 and 124 may be used aswell. Reinforcement belts 122 and 124 also do not intersect theequatorial plane EP of tire 100 and, instead, are positioned inessentially identical fashion on both sides of the equatorial plane andnear the top of sidewall portions 108.

As shown, reinforcement belts 122 and 124 are spaced apart along theaxial direction and, in fact, extend to an axial width that is greaterthan e.g., belt 118, and plies 120 and 131. While other widths may beused, in one preferred embodiment of the invention reinforcement belts122 and 124 extend to an axial width that is between about 86 percent toabout 110 percent of the rolling tread width of tire 100. In stillanother embodiment, reinforcement belts 122 and 124 extend along theaxial width of the tire by a distance that is between about 0 to about40 mm greater than the axial width of the working ply 131. Also, for theembodiment of FIG. 1, the axially-inner ends 123 of reinforcement belts122 and 124 is axially outside of the ends 129 of reinforcement belt130.

The carcass 106 of tire 100 is constructed according to an equilibriumcurve that is flat along the summit 110 of the tire. In turn, as shownin FIG. 1, when tire 100 is inflated to its normal operating pressure,reinforcement belts 122, 124 and 130 have a straight profile within ameridian plane of the tire as shown in FIG. 1. As a result, tire 100 haslittle or no droop as previously discussed.

Along the sidewalls of tire 100, carcass 106 is constructed according toan equilibrium curve that is shown in FIG. 6. The equilibrium curveincludes a first part 180 that begins at equator 190 and extendsupwardly towards the summit of the tire where it becomes tangent to theaxial direction (i.e. tangent to a line parallel to the x-axis). Thesecond part 200 of the equilibrium curve also begins at equator 190 andextends downwardly towards the bead section of tire.

The equilibrium curve in the sidewalls of tire 100 as shown in FIG. 6can be characterized by 2 parameters: Rc, the center radius, and Re, theequator radius. The equilibrium curve can be described by a differentialequation and can also be unambiguiously constructed starting from thecenter radius by calculating the tangent angle ⊥ and curvature P of thecurve at each subsequent radius. The expressions for the tangent angleand curvature for a radial equilibrium curve are well known to one ofskill in the art and are given as follows:

$\begin{matrix}{{\sin \mspace{14mu} \phi} = \frac{\left( {r^{2} - r_{e}^{2}} \right)}{\left( {r_{c}^{2} - r_{e}^{2}} \right)}} & (1) \\{\kappa = \frac{2r}{\left( {r_{c}^{2} - r_{e}^{2}} \right)}} & (2)\end{matrix}$

where the center radius r_(c) and the equator radius r_(e) areparameters which depend upon, e.g., the dimension of the tire beingdesigned. In the example given in FIG. 6, r_(c)=480 mm and r_(e)=400 mm.

FIG. 2 provides another exemplary embodiment of tire 100 according tothe present invention where the same reference numerals as used in FIG.1 indicate the same or similar components as FIG. 1. In the exemplaryembodiment of FIG. 2, tire 100 includes two reinforcement belts 114 and116 that each extend between sidewall portions 108, through the summit110, and intersect the equatorial plane EP. Reinforcement belts 114 and116 are each positioned radially outside of working ply 128 and radiallyinside of tread portion 112. Another working ply 126 is positionedradially outside of breaker belt 118 but radially inside of working ply128.

As shown, reinforcement belts 114 and 116 extend along the axialdirection and, in fact, extend to an axial width that is greater thane.g., belt 118, and plies 126 and 128. While other widths may be used,in one preferred embodiment of the invention the axially outermost ends125 of reinforcement belts 114 and 116 extend to an axial width thatthat is between about 86 percent to about 110 percent of the rollingtread width of tire 100. In still another embodiment, the axiallyoutermost ends 125 of reinforcement belts 114 and 116 extend along theaxial width of the tire by a distance that is between about 0 to about40 mm greater than the axial width of the working ply 128.

In a manner similar to the embodiment of FIG. 1, the carcass 106 of tire100 is constructed according to an equilibrium curve that is flat alongthe summit 110 of the tire. In turn, as shown in FIG. 2, when tire 100is inflated to its normal operating pressure, reinforcement belts 114and 116 have a straight profile within a meridian plane of the tire asshown in FIG. 2. As a result, tire 100 has little or no droop aspreviously discussed. Along the sidewalls of tire 100 of FIG. 2, carcass106 is constructed according to an equilibrium curve as described abovewith regard to FIG. 1 and as shown in FIG. 6.

As stated above, tire 100 of the exemplary embodiments of both FIGS. 1and 2 is constructed according to an equilibrium curve as described. Aswill be understood by one of ordinary skill in the art using theteachings disclosed herein, “constructed according to an equilibriumcurve” means the tire is constructed such that carcass 106 assumessubstantially the shape of such curve when tire 100 is properly inflatedand allows for adjustments to the actual shape of the curve as may bedeveloped during design of the tire by e.g., finite element analysisand/or other computational methods.

For the exemplary embodiments of FIGS. 1 and 2, reinforcement belts 114,116, 122, 124, and 130 are each constructed from a plurality ofcircumferentially-oriented cables that are either parallel to theequatorial plane EP or within the range of 0 to 5 degrees from theequatorial plane EP. Preferably, the cables are continuous about thecircumference of the tire and are constructed from steel that can bereferred to as semi-elastic in that the cables have elongations at breakof greater than 2 percent. In addition, preferably the cables arebi-modular—i.e. on a curve representing the tensile stress as a functionof relative elongation, the curve has shallow gradients for lowelongation and a substantially constant, steep gradient for higherelongation. Also, the cables have a very low modulus before curing, forelongations of less than 2 percent, which makes it possible to increasethe circumferential development of belts 114, 116, 122, 124, and 130during curing of the tire. Alternatively, other constructions such ashigh elongation cable or steel monofilament, or other materials, such astextile or aramid, etc. may be used as well.

A variety of shapes along the circumferential direction may be used forthe cables located in reinforcing reinforcement belts 114, 116, 122,124, and 130. For example, the cables may have a wavy configuration asshown in FIG. 2 of EP 0980770. Zig-zag may also be used in certainapplications. In fact, using the teachings disclosed herein, one ofskill in the art will understand that other constructions for the cablesin these reinforcement belts may also be used.

A tire constructed according to the exemplary embodiments describedherein, particularly a wider tire, can have several performanceadvantages such as e.g., improvements in tread wear that can beattributed at least in part to the absence of droop. FIG. 3A, forexample, provides a plot of simulated, cable tension data for aproduction tire (PT) of size 445/50 R22.5 that does not includereinforcement belts that are flat or that have a straight profile alonga meridian plane of the tire. Also included is simulated data for cabletensions in the reinforcement belts 122, 124, and 130 of the exemplaryembodiment of FIG. 1. Both the maximum (max) and minimum (min) cabletensions that result as the tire is rotated one complete revolution aredepicted including data for the left (l) and right (r) sides for belts122 and 124. The center of the plot, i.e. where the x-axis is zero,represents the center or equatorial plane EP of the tire.

As shown by the data simulation, the average cable tension is much lowerfor the exemplary embodiment of FIG. 1 than the production tire. Thehighest cable tension experienced in belts 122, 124, and 130 is alsosignificantly lower than the highest cable tension for the productiontire.

Similarly, FIG. 3B provides a plot of simulated, cable tension data fora production tire (PT) of size 445/50 R22.5 that does not includereinforcement belts that are flat or that have a straight profile alonga meridian plane of the tire. Also included is simulated data for cabletension in the reinforcement belts 114 and 116 of the exemplaryembodiment of FIG. 2. Again, as shown by the data simulation, theaverage cable tension is much lower for the exemplary embodiment of FIG.2 than the production tire. The highest cable tension experienced inbelts 114 and 116 is also significantly lower than the highest cabletension for the production tire.

FIG. 4 provides another plot of simulated data comparing the embodimentsof FIGS. 1 and 2 with the production tire. Over a substantial range ofloads, the embodiments of FIGS. 1 and 2 provide a vertical stiffness,Kz, that is substantially greater than the production tire. Again, thishigher stiffness helps provide, e.g., improvements in tread wear.

With the help again of simulated data, FIG. 5 provides several plots ofthe footprints 202, 204, 206, 208, and 210 that are obtained at variousloads for a tire constructed according to the exemplary embodiment ofFIG. 1 and corresponds to the loads shown in FIG. 4. As will berecognized by one of skill in the art, these footprints providesubstantial improvement in that their shape overall approaches that of arectangle, which is good for tread wear performance. The production tirePT does not provide shapes that are as rectangular. Additionally, theshoulder ribs of the tread portion of the tire maintain most of theirsurface in contact with the ground even at lighter loads.

It should be understood that for the exemplary embodiments of FIGS. 1and 2, additional reinforcing belts (with e.g.,circumferentially-oriented cables as described) of various widths andconfigurations can be added to either embodiment to yield still furtherembodiments of the invention. Additionally, the present invention alsoincludes embodiments having a single reinforcing belt have axially outerends that extend to the shoulder portions of the tire. Such singlereinforcing belt may intersect the equatorial plane of the tire or maybe constructed of two portions positioned on opposing sides of theequatorial plane without intersection.

While the present subject matter has been described in detail withrespect to specific exemplary embodiments and methods thereof, it willbe appreciated that those skilled in the art, upon attaining anunderstanding of the foregoing may readily produce alterations to,variations of, and equivalents to such embodiments. Accordingly, thescope of the present disclosure is by way of example rather than by wayof limitation, and the subject disclosure does not preclude inclusion ofsuch modifications, variations and/or additions to the present subjectmatter as would be readily apparent to one of ordinary skill in the art.

What is claimed is:
 1. A tire defining axial, circumferential, and radial directions, the tire defining a meridian plane and having a summit region positioned between sidewall portions of the tire, the tire comprising: a carcass extending between the sidewall portions and through the summit region of the tire; a working ply positioned radially outside of said carcass and extending along the axial direction of the tire; at least one reinforcement belt positioned radially outside of said carcass and positioned in the summit region of the tire, said at least one reinforcement belt having at least one axially outer end that extends to one sidewall portion of the tire and another outer end extending to the other sidewall portion of the tire, said reinforcement belt comprising a plurality of circumferentially-oriented cables, said reinforcement belt having a flat profile within a meridian plane of the tire; and, a tread portion positioned radially outside of said reinforcement belts and extending through the summit region and between the sidewall portions of the tire.
 2. The tire as in claim 1, the tire defining an equatorial plane, and wherein said reinforcement belt comprises two portions, each portion positioned in an opposing manner about the equatorial plane and without intersecting the equatorial plane.
 3. The tire as in claim 1, the tire defining an equatorial plane, and wherein said reinforcement belt intersects the equatorial plane.
 4. The tire as in claim 1, the tire defining an equatorial plane, wherein said circumferentially-oriented cables are at angle in the range of 0 to about +/- 5 degrees from the equatorial plane. 